AZURE SD: Validate HTTP config

Related-to #12810

Signed-off-by: Jayapriya Pai <janantha@redhat.com>

config/config_test.go

@@ -1769,6 +1769,10 @@ var expectedErrors = []struct {
 		filename: "azure_authentication_method.bad.yml",
 		errMsg:   "unknown authentication_type \"invalid\". Supported types are \"OAuth\" or \"ManagedIdentity\"",
 	},
+	{
+		filename: "azure_bearertoken_basicauth.bad.yml",
+		errMsg:   "at most one of basic_auth, oauth2, bearer_token & bearer_token_file must be configured",
+	},
 	{
 		filename: "empty_scrape_config.bad.yml",
 		errMsg:   "empty or null scrape config section",

config/testdata/azure_bearertoken_basicauth.bad.yml

@@ -0,0 +1,11 @@
+scrape_configs:
+  - job_name: prometheus
+    azure_sd_configs:
+      - subscription_id: 11AAAA11-A11A-111A-A111-1111A1111A11
+        tenant_id: BBBB222B-B2B2-2B22-B222-2BB2222BB2B2
+        client_id: 333333CC-3C33-3333-CCC3-33C3CCCCC33C
+        client_secret: mysecret
+        bearer_token: 1234
+        basic_auth:
+          username: user
+          password: password

discovery/azure/azure.go

@@ -144,7 +144,7 @@ func (c *SDConfig) UnmarshalYAML(unmarshal func(interface{}) error) error {
 		return fmt.Errorf("unknown authentication_type %q. Supported types are %q or %q", c.AuthenticationMethod, authMethodOAuth, authMethodManagedIdentity)
 	}
 
-	return nil
+	return c.HTTPClientConfig.Validate()
 }
 
 type Discovery struct {